1. Field of the Invention
The present invention relates to a medical adsorbent for oral administration comprising activated carbon obtained using a spherical phenol resin as the starting material.
2. Background Art
Medicinal carbon listed in the Japanese Pharmacopeia has conventionally been used for treatment of acute toxicant or drug poisoning and gastrointestinal disease. Such medicinal carbon is usually activated carbon powder obtained using wood or the like as the main starting material, and a curative effect is exhibited because the medicinal carbon adsorbs harmful substances in the gastrointestinal tract and is excreted out of the body while retaining the harmful substances.
Incidentally, since the aforementioned activated carbon powder used as medicinal carbon is simply pulverized, the shapes of the individual particles are non-uniform and therefore the enteric flow property is poor, such that side-effects such as constipation occur after ingestion. Activated carbon is also unsatisfactory because it is generally highly hydrophobic and unsuited for adsorption of ionic organic compounds such as arginine and putrescine, as typical causative substances of uremia or their precursors.
Among attempts to solve these problems there have been disclosed anti-nephrosis agents comprising activated carbon obtained from materials which are resin compounds in spherical or other shapes formed from wood or petroleum- or coal-based pitches and the like as starting materials (for example, Patent Document 1). This activated carbon is prepared using petroleum-based hydrocarbons (pitch) as the starting material and is adjusted to a relatively uniform particle size and then subjected to carbonization and activation. There has also been disclosed an adsorbent for oral administration wherein it is attempted to render the particle sizes of the activated carbon itself relatively uniform while also adjusting the distribution of the pore volume, etc. in the activated carbon (see Patent Document 2). Such medicinal activated carbon which has been obtained with relatively uniform particle sizes and improved enteric flow properties, and activated carbon with enhanced adsorption properties by adjustment of the pores, is administered to a great number of mild chronic renal insufficiency patients.
Medicinal activated carbon must be able to rapidly and efficiently adsorb causative substances of uremia or their precursors. With existing medicinal activated carbon, however, it has been difficult to reduce the particle sizes while maintaining spherical shapes. Also, adjustment of the pores of conventional medicinal activated carbon has been less than satisfactory while the adsorption performance is not always sufficient, and therefore higher daily doses of administration are required. In particular, because chronic renal insufficiency patients are restricted in their intake of water, it has been a major grievance for patients to swallow their doses with small amounts of water.
In addition, the gastrointestinal organs such as the stomach and small intestines are an environment in which various different substances are mixed including compounds-essential to physiological function such as sugars, proteins, and enzymes secreted by the intestinal walls. Medicinal activated carbon therefore preferably has a selective adsorption function which inhibits adsorption of compounds which are essential to physiological function while adsorbing causative substances of uremia.
[Patent Document 1] Japanese Unexamined Patent Publication HEI No. 6-135841 (page 2)
[Patent Document 2] Japanese Unexamined Patent Publication No. 2002-308785 (pages 2-6)